1. Field of the Invention
The invention relates to the treatment of foundry wastes, particularly core and molding sand, so as to reclaim this discarded sand for new core manufacture in the foundry.
2. Description of the Prior Art
Practically all new foundry sand input is used to make cores, which are bonded constructions placed in molds to provide casting voids. The core mold consists of sand bonded with special additives including organic binders. A solidified casting is removed from the mold by vibration which breaks down the sand mold as well as some of the core, the latter also being partially disintegrated by the heat from the mold and metal. The disintegrated core sand enters the molding sand system which is recycled many times, but an equivalent quantity is displaced and must be discarded. Unbroken cores as well as core scrap produced in the core making and curing steps are also discarded. Disposal of this scrap creates both economic and ecological problems and it is therefore desirable to upgrade and reclaim these scrap streams to new sand quality for entry at the core making point.
Problems in reclamation of discarded sand involve both quality level and uniformity. Representative of prior methods are those disclosed in Connolly U.S. Pat. No. 2,478,461, Christensen U.S. Pat. No. 2,420,392, Will U.S. Pat. No. 2,783,511, and Muller U.S. Pat. No. 2,835,941. The Connolly patent discusses the reclaiming of foundry sand by heating or roasting treatment which causes the carbonaceous material to be burned away. The temperatures discussed in this patent are up to 1200.degree. to 1500.degree. F. The other patents describe different reclaiming treatments having various deficiencies with the present invention overcomes. Other prior patents pertinent to the treatment of foundry sand by methods different than that of the present invention are Norton U.S. Pat. No. 2,041,721, Poulsen U.S. Pat. No. 1,052,514 and Zifferer U.S. Pat. No. 3,683,995. None of the above mentioned patents disclose the heat treating method described in the claims in this application with its attendant advantages.